Such an assembly is described, for example, in Document EP-A-1 232 932.
The structure described in that document makes it possible for the visible outlines of the headlight units to be positioned automatically and permanently relative to the corresponding fender ends and relative to the bumper skin. At the same time, that structure guarantees that the bumper skin is positioned accurately relative to the fender ends.
On certain vehicles, it is chosen for the fender front portions to be made of a plastics material rather than of sheet metal. Such a choice of technology, which offers certain advantages, nevertheless results in the fender front portions undergoing relatively considerable deformation over the life of the vehicle. In certain preferred directions of deformation, such as the longitudinal direction of the fender of the vehicle, such deformation can be of the order of a few millimeters, whereas it is not significant when the fenders are made of metal.
Via the connection existing between the fender front portion and the corresponding beam, such deformation can, after the front portion assembly of the vehicle has been assembled, and during the life of the vehicle, give rise to significant deformation of the beam, and thereby cause uncontrollable misadjustment of the orientation and of the position of the headlight unit supported by the beam.